In general, developer powder is mainly used in an electrophotographic image forming apparatus, such as a copy machine, a printer, and a facsimile machine. An electrostatic latent image may be formed on an image bearing member, such as a photosensitive drum. Developer may be used to coat the image bearing member to form a toner image. The toner image is then transferred onto a recording medium, such as paper. A fixing process may be performed to fix the image to the recording medium.
Developer can be broadly classified into a multi-component developer, a two-component developer may include toner and carrier, and a single-component developer may include magnetic toner. A developer regulating member such as a regulating blade, is provided to promote frictional electrification of the developer on a developer bearing member. The developer regulating member may be formed only of a magnetic member. Alternatively, the developer regulating member may include a non-magnetic member as a base member and a magnetic member disposed in an area (e.g., developer regulating area) where the magnetic member faces the developer bearing member.
In a developing device including the above-described developer regulating member, a part of the developer supplied to the developer regulating area passes through the developer regulating member and forms a developer layer on the developer bearing member as the developer bearing member rotates. However, most of the developer supplied to the developer regulating area is blocked by the developer regulating member and is returned to the inside of the developing device. At this time, the developer blocked by the developer regulating member, tends to move toward the ends of the developer bearing member and the developer regulating member in the longitudinal direction thereof. Therefore, it is necessary to prevent the developer from leaking from the developing device at the ends of the developer bearing member and the developer regulating member.
Accordingly, a method for inhibiting leakage of the developer by providing a magnetic sealing member at each end of the developing device in the longitudinal direction thereof has been proposed. According to this method, the leakage of the developer is prevented by using a magnetic brush formed between the magnetic sealing member and the developer bearing member due to a magnetic field between a magnet poles disposed in the developer bearing member and the magnetic sealing member.
The leakage of developer has been prevented using only a magnetic sealing member. As is shown in FIG. 1, depicting a developing device, a magnetic sealing member 101 is fixed to an inner surface of a housing of the developing device at each end prior to use. Thus, the structure is designed such that a gap G2 is provided between the magnetic sealing member 101 and a developer regulating member 104, so that the magnetic sealing member 101 does not interfere with the developer regulating member 104 in the process of attaching the developer regulating member 104. However, in this structure, the direction in which the developer moves from a central area of the developer bearing member to the end thereof (direction shown by the arrow B) coincides with the direction in which the gap G2 extends. Therefore, even if the gap G2 is filled with a magnetic brush formed between the magnetic sealing member 101 and the developer bearing member, the developer easily leaks through the gap G2.
The leakage of the toner at the ends of the developer bearing member can also be prevented by placing a spacer which fills a gap between a developing roller and an end sealing member at each end of the developer bearing member. Therefore, also in the structure including the magnetic sealing member, an auxiliary sealing member (spacer) made of sponge-like elastic body, nonwoven fabric, etc., may be additionally used to prevent the leakage of the developer through a space between an end face of the developer regulating member and a contact surface of the magnetic sealing member. Such a structure is shown in FIG. 2.
Referring to FIG. 2, a magnetic sealing member 101 is positioned upstream of a position where a developer bearing member 102 and a developer regulating member 104 face each other in a rotational direction of the developer bearing member 102 (direction shown by the arrow A). A magnet member 103 having a plurality of magnet poles is disposed in the developer bearing member 102. An auxiliary sealing member 105 made of, for example, sponge, is wound around the developer regulating member 104. An end portion of the magnetic sealing member 101 in the longitudinal direction thereof is in contact with the auxiliary sealing member 105, so that the leakage of the developer through the gap between the magnetic sealing member 101 and the developer regulating member 104 is prevented.
As shown in FIG. 3, an auxiliary sealing member 105 will be attached at a position displaced toward the inside of the developing device (toward the front in FIG. 3). In such a case, the developer which moves along the longitudinal direction of the developer bearing member 102 in the direction shown by the arrow B from the central area of the developer bearing member 102 toward the end thereof is blocked by the magnetic sealing member 101, and the developer which flows downstream in the rotational direction of the developer bearing member 102 (direction shown by the arrow A) due to the rotation of the developer bearing member 102 is blocked by the auxiliary sealing member 105. Therefore, a large load is applied to the auxiliary sealing member 105, and the life of the auxiliary sealing member 105 is considerably reduced. To prevent this, the auxiliary sealing member 105 must be attached with high accuracy. Therefore, the assembly process of the developing device is complex and difficult.
The leakage of the developer may also be prevented by a method using only the magnetic sealing member. In this method, a magnetic member is disposed on a non-contact surface of an elastic developer regulating member, and a magnet is disposed on a portion of a developer container which faces the elastic developer regulating member such that the magnet is spaced from the magnetic member by a predetermined distance, so that a magnetic brush is also formed between the developer container and the elastic developer regulating member.